U.S. patent application number 13/720051 was filed with the patent office on 2013-06-20 for semiconductor devices connected by anisotropic conductive film comprising conductive microspheres.
The applicant listed for this patent is Hyun Min CHOI, Nam Ju KIM, Kyoung Soo PARK, Young Woo PARK, Joon Mo SEO, Motohide TAKEICHI, Dong Seon UH, Arum YU. Invention is credited to Hyun Min CHOI, Nam Ju KIM, Kyoung Soo PARK, Young Woo PARK, Joon Mo SEO, Motohide TAKEICHI, Dong Seon UH, Arum YU.
Application Number | 20130154095 13/720051 |
Document ID | / |
Family ID | 48609290 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130154095 |
Kind Code |
A1 |
YU; Arum ; et al. |
June 20, 2013 |
SEMICONDUCTOR DEVICES CONNECTED BY ANISOTROPIC CONDUCTIVE FILM
COMPRISING CONDUCTIVE MICROSPHERES
Abstract
A semiconductor device includes an anisotropic conductive film
for connecting the semiconductor device. The anisotropic conductive
film includes a first conductive layer that has first conductive
particles. The first conductive particles include cores containing
silica or a silica composite, and have a 20% K-value ranging from
about 7,000 N/mm.sup.2 to about 12,000 N/mm.sup.2.
Inventors: |
YU; Arum; (Uiwang-si,
KR) ; KIM; Nam Ju; (Uiwang-si, KR) ; PARK;
Kyoung Soo; (Uiwang-si, KR) ; PARK; Young Woo;
(Uiwang-si, KR) ; SEO; Joon Mo; (Uiwang-si,
KR) ; TAKEICHI; Motohide; (Uiwang-si, KR) ;
UH; Dong Seon; (Uiwang-si, KR) ; CHOI; Hyun Min;
(Uiwang-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YU; Arum
KIM; Nam Ju
PARK; Kyoung Soo
PARK; Young Woo
SEO; Joon Mo
TAKEICHI; Motohide
UH; Dong Seon
CHOI; Hyun Min |
Uiwang-si
Uiwang-si
Uiwang-si
Uiwang-si
Uiwang-si
Uiwang-si
Uiwang-si
Uiwang-si |
|
KR
KR
KR
KR
KR
KR
KR
KR |
|
|
Family ID: |
48609290 |
Appl. No.: |
13/720051 |
Filed: |
December 19, 2012 |
Current U.S.
Class: |
257/746 |
Current CPC
Class: |
H01L 2224/16225
20130101; H01L 2924/12041 20130101; H01L 2224/29344 20130101; H01L
2224/29301 20130101; H01L 24/32 20130101; H01L 2924/15788 20130101;
H01L 2224/29082 20130101; H01L 2224/83101 20130101; H01L 2224/29398
20130101; H01L 2224/29386 20130101; H01L 24/29 20130101; H01L
2924/07802 20130101; H01L 2924/12044 20130101; H01L 2224/29447
20130101; H01L 2924/12041 20130101; H01L 2224/83193 20130101; H01L
2224/29393 20130101; H01L 2224/83203 20130101; H01L 2224/83851
20130101; H01L 2924/20106 20130101; H01L 24/83 20130101; H01L
2224/29355 20130101; H01L 24/13 20130101; H01L 2924/15788 20130101;
H01L 2224/29439 20130101; H01L 2224/13144 20130101; H01L 2224/29339
20130101; H01L 2224/29444 20130101; H01L 2224/73204 20130101; H01L
2224/29455 20130101; H01L 2224/2929 20130101; H01L 2224/29401
20130101; H01L 24/73 20130101; H01L 2224/29301 20130101; H01L
2224/29347 20130101; H01L 2224/29401 20130101; H01L 2224/29464
20130101; H01L 2224/32225 20130101; H01L 2224/73204 20130101; H01L
2224/2939 20130101; H01L 2924/07802 20130101; H01L 2924/12044
20130101; H01L 2224/13144 20130101; H01L 2924/00014 20130101; H01L
2224/16225 20130101; H01L 2924/00 20130101; H01L 2924/00 20130101;
H01L 2924/00 20130101; H01L 2924/00 20130101; H01L 2924/014
20130101; H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L
2924/00014 20130101; H01L 2924/014 20130101; H01L 2224/32225
20130101 |
Class at
Publication: |
257/746 |
International
Class: |
H01L 23/00 20060101
H01L023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2011 |
KR |
10-2011-0138246 |
Claims
1. A semiconductor device, comprising: an anisotropic conductive
film for connecting the semiconductor device, the anisotropic
conductive film including: a first conductive layer having first
conductive particles, the first conductive particles including
cores containing silica or a silica composite, and having a 20%
K-value ranging from about 7,000 N/mm.sup.2 to about 12,000
N/mm.sup.2.
2. The semiconductor device as claimed in claim 1, wherein the
first conductive particles have a compressive strain ranging from
about 5% to about 40% upon thermal compression of the anisotropic
conductive film under conditions of 220.degree. C. and 110 Mpa for
5 seconds.
3. The semiconductor device as claimed in claim 1, wherein the
cores include the silica composite, the silica composite including
a polymer resin and silica, the polymer resin being a polymer of at
least one monomer selected from the group of a crosslinking
polymerizable monomer and a mono-functional monomer.
4. The semiconductor device as claimed in claim 3, wherein the
polymer resin includes the crosslinking polymerizable monomer, the
crosslinking polymerizable monomer including at least one selected
from the group of a vinyl benzene monomer, allyl compound monomer
and an acrylate monomer.
5. The semiconductor device as claimed in claim 3, wherein the
polymer resin includes the mono-functional monomer, the
mono-functional monomer including at least one selected from the
group of a styrene monomer, a (meth)acrylate monomer, vinyl
chloride, vinyl acetate, vinyl ether, vinyl propionate, and vinyl
butyrate.
6. The semiconductor device according as claimed in claim 3,
wherein the silica composite includes about 15 wt % to about 90 wt
% of silica based on a total amount of the silica composite.
7. The semiconductor device as claimed in claim 1, wherein the
first conductive particles have an average particle diameter of
about 0.1 .mu.m to about 200 .mu.m.
8. The semiconductor device according as claimed in claim 1,
wherein the first conductive particles include conductive shells on
the cores.
9. The semiconductor device as claimed in claim 1, wherein the
first conductive particles have protrusions on surfaces
thereof.
10. The semiconductor device as claimed in claim 1, wherein: the
anisotropic conductive film further includes second conductive
particles having a second 20% K-value different from the 20%
K-value of the first conductive particles, the second 20% K-value
ranging from about 3,000 N/mm.sup.2 to about 7,000 N/mm.sup.2, and
a difference between the 20% K-value of the first conductive
particles and the second 20% K-value of the second conductive
particles is less than about 5,000 N/mm.sup.2.
11. The semiconductor device as claimed in claim 10, wherein the
second conductive particles have cores including a polymer
resin.
12. The semiconductor device as claimed in claim 10, wherein the
first conductive particles have about 10 to about 40 protrusions
per unit surface area on surfaces thereof.
13. The semiconductor device as claimed in claim 10, wherein the
second conductive particles have 0 to about 10 protrusions per unit
surface area on surfaces thereof.
14. The semiconductor device as claimed in claim 10, wherein the
second conductive particles are present in an amount of about 1 to
about 30 parts by weight based on 100 parts by weight of a total
amount of conductive particles.
15. The semiconductor device as claimed in claim 1, wherein: the
anisotropic conductive film further includes a second conductive
layer on the first conductive layer, and the second conductive
layer includes second conductive particles, a first hardness of the
first conductive particles being higher that a second hardness of
the second conductive particles.
16. The semiconductor device as claimed in claim 15, wherein a
difference between the 20% K-value of the first conductive
particles and a second 20% K-value of the second conductive
particles is about 5,000 N/mm.sup.2 or more.
17. The semiconductor device as claimed in claim 1, wherein: the
anisotropic conductive film further includes a second conductive
layer on the first conductive layer, and a first surface roughness
of the first conductive particles is greater that a second surface
roughness of the second conductive particles.
18. A semiconductor device, comprising: a wiring substrate having a
metal and metal oxide layer placed on an outermost layer thereof;
an anisotropic conductive film attached to a chip mounting surface
of the wiring substrate; and a semiconductor chip mounted on the
anisotropic conductive film, wherein: the anisotropic conductive
film directly adjoins the metal and metal oxide layer and includes
a first conductive layer including first conductive particles, and
the first conductive particles have a 20% K-value from about 7,000
N/mm.sup.2 to about 12,000 N/mm.sup.2, and have a compressive
strain from about 5% to about 40% upon thermal compression of the
anisotropic conductive film under conditions of 220.degree. C. and
110 Mpa for 5 seconds.
19. The semiconductor device as claimed in claim 18, wherein the
anisotropic conductive film further includes second conductive
particles having a second 20% K-value that is lower than the 20%
K-value of the first conductive particles.
20. The semiconductor device as claimed in claim 18, wherein the
anisotropic conductive film includes a second conductive layer on
the first conductive layer, the second conductive layer including
second conductive particles that have a second 20% K-value that is
lower than the 20% K-value of the first conductive particles.
21. The semiconductor device as claimed in claim 18, wherein the
first conductive particles include protrusions on surfaces thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.119
to Korean Patent Application No. 10-2011-0138246 filed on Dec. 20,
2011, in the Korean Intellectual Property Office, and entitled:
"Semiconductor Devices Connected by Anisotropic Conductive Film
Comprising Conductive Microspheres," which is incorporated by
reference herein in its entirety.
BACKGROUND
[0002] Anisotropic conductive adhesives may be used to connect
electronic components such as semiconductor devices to a circuit
board. For example, the anisotropic conductive adhesives may be
used for forming connections in various displays such as liquid
crystal displays (LCDs) and organic light-emitting devices
(OLEDs).
SUMMARY
[0003] Embodiments may be realized by providing a semiconductor
device that includes an anisotropic conductive film for connecting
the semiconductor device, and the anisotropic conductive film
includes a first conductive layer having first conductive
particles. The first conductive particles include cores containing
silica or a silica composite, and have a 20% K value ranging from
about 7,000 N/mm.sup.2 to about 12,000 N/mm.sup.2.
[0004] The first conductive particles may have a compressive strain
ranging from about 5% to about 40% upon thermal compression of the
anisotropic conductive film under conditions of 220.degree. C. and
110 Mpa for 5 seconds. The cores may include the silica composite
and the silica composite may include a polymer resin and silica.
The polymer resin may be a polymer of at least one monomer selected
from the group of a crosslinking polymerizable monomer and a
mono-functional monomer.
[0005] The polymer resin may include the crosslinking polymerizable
monomer, and the crosslinking polymerizable monomer may include at
least one selected from the group of a vinyl benzene monomer, allyl
compound monomer and an acrylate monomer. The polymer resin may
include the mono-functional monomer, and the mono-functional
monomer may include at least one selected from the group of a
styrene monomer, a (meth)acrylate monomer, vinyl chloride, vinyl
acetate, vinyl ether, vinyl propionate, and vinyl butyrate.
[0006] The silica composite may include about 15 wt % to about 90
wt % of silica based on a total amount of the silica composite. The
first conductive particles may have an average particle diameter of
about 0.1 .mu.m to about 200 .mu.m. The first conductive particles
may include conductive shells on the cores. The first conductive
particles may have protrusions on surfaces thereof.
[0007] The anisotropic conductive film may further include second
conductive particles having a second 20% K-value different from the
20% K-value of the first conductive particles, and the second 20%
K-value may range from about 3,000 N/mm.sup.2 to about 7,000
N/mm.sup.2. A difference between the 20% K-value of the first
conductive particles and the second 20% K-value of the second
conductive particles may be less than about 5,000 N/mm.sup.2.
[0008] The second conductive particles may have cores including a
polymer resin. The first conductive particles may have about 10 to
about 40 protrusions per unit surface area on surfaces thereof. The
second conductive particles may have 0 to about 10 protrusions per
unit surface area on surfaces thereof. The second conductive
particles may be present in an amount of about 1 to about 30 parts
by weight based on 100 parts by weight of a total amount of
conductive particles.
[0009] The anisotropic conductive film may further include a second
conductive layer on the first conductive layer. The second
conductive layer may include second conductive particles, and a
first hardness of the first conductive particles may be higher that
a second hardness of the second conductive particles. A difference
between the 20% K-value of the first conductive particles and a
second 20% K-value of the second conductive particles may be about
5,000 N/mm.sup.2 or more. A first surface roughness of the first
conductive particles may be greater that a second surface roughness
of the second conductive particles.
[0010] Embodiments may also be realized by providing a
semiconductor device that includes a wiring substrate having a
metal and metal oxide layer placed on an outermost layer thereof,
an anisotropic conductive film attached to a chip mounting surface
of the wiring substrate, and a semiconductor chip mounted on the
anisotropic conductive film. The anisotropic conductive film
directly adjoins the metal and metal oxide layer and includes a
first conductive layer including first conductive particles, and
the first conductive particles have a 20% K-value from about 7,000
N/mm.sup.2 to about 12,000 N/mm.sup.2, and have a compressive
strain from about 5% to about 40% upon thermal compression of the
anisotropic conductive film under conditions of 220.degree. C. and
110 Mpa for 5 seconds.
[0011] The anisotropic conductive film may further include second
conductive particles having a second 20% K value that is lower than
the 20% K value of the first conductive particles. The anisotropic
conductive film may include a second conductive layer on the first
conductive layer, and the second conductive layer may include
second conductive particles that have a second 20% K-value that is
lower than the 20% K value of the first conductive particles. The
first conductive particles may include protrusions on surfaces
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Features will become apparent to those skilled in the art by
describing in detail exemplary embodiments with reference to the
attached drawings in which:
[0013] FIG. 1 illustrates first conductive particles having high
hardness to provide low deformability and second conductive
particles having low hardness to provide good visibility, in which
a right side picture is an enlarged view of a left side
picture;
[0014] FIG. 2 illustrates evaluation results of Experimental
Example 2;
[0015] FIG. 3 illustrates an explanation of a measurement apparatus
for measuring hardness of conductive particles using a
nano-indenter;
[0016] FIG. 4 illustrates an image of first conductive particles
having high surface roughness in accordance with an exemplary
embodiment;
[0017] FIG. 5 illustrates an image of second conductive particles
having low surface roughness in accordance with an exemplary
embodiment;
[0018] FIG. 6 illustrates an image of one example of conductive
particles exhibiting good post-bonding visibility (Example 4);
and
[0019] FIG. 7 illustrates an image of one example of conductive
particles exhibiting poor post-bonding visibility (Comparative
Example 8).
[0020] FIGS. 8 and 9 illustrate exemplary embodiments of
anisotropic conductive films.
DETAILED DESCRIPTION
[0021] Example embodiments will now be described more fully
hereinafter with reference to the accompanying drawings; however,
they may be embodied in different forms and should not be construed
as limited to the embodiments set forth herein. Rather, these
embodiments are provided so that this disclosure will be thorough
and complete, and will fully convey exemplary implementations to
those skilled in the art.
[0022] An exemplary embodiment includes a semiconductor device
connected by an anisotropic conductive film, in which the
anisotropic conductive film may include a first conductive layer
having first conductive particles. The first conductive particles
may include cores that contain silica and/or a silica composite,
and the first conductive particles may have a 20% K-value ranging
from about 7,000 N/mm.sup.2 to about 12,000 N/mm.sup.2.
[0023] According to an exemplary embodiment, a hardness
characteristic of conductive particles will be expressed by a
K-value. Determining the hardness may include obtaining a load upon
deformation of a single conductive particle using a nano-indenter
(see FIG. 3) and calculating the K-value based on the load
according to Equation 1
K-value(N/mm.sup.2)=(3/2.sup.1/2)FS.sup.-3/2R.sup.-1/2 [Equation
1]
[0024] wherein F is a load (e.g., in Newtons) upon compressive
deformation of a conductive particle, S is a compressive
displacement (e.g., mm) of the conductive particle upon compression
deformation thereof, and R is a radius (e.g., mm) of the conductive
particle.
[0025] As used herein, the term "20% K-value" means the K-value
when S/2R=0.2.
[0026] According to an exemplary embodiment, the first conductive
particles have a 20% K-value ranging from about 7,000 N/mm.sup.2 to
about 12,000 N/mm.sup.2, e.g., from about 8,000 N/mm.sup.2 to about
11,000 N/mm.sup.2. However, embodiments are not limited thereto,
e.g., the 20% K-value may range from about 9,500 N/mm.sup.2 to
about 10,500 N/mm.sup.2, from about 9,000 N/mm.sup.2 to about
11,000 N/mm.sup.2, etc.
[0027] Within this range of the 20% K-value, it may be possible to
obtain conductive particles that have sufficient hardness to
penetrate a metal oxide layer for connection and to obtain high
hardness conductive particles that exhibit slight deformability.
For example, the first conductive particles may have a compressive
strain of about 5% to about 40% upon thermal compression under
conditions of, e.g., 220.degree. C. and 110 MPa for 5 seconds.
[0028] The radius R of the conductive particle may be an initial
radius. For example, the radius R may be measured before
deformation of the single conductive particle.
[0029] According to an exemplary embodiment, the first conductive
particles may include any core allowing the conductive particles to
have a 20% K-value of about 7,000 N/mm.sup.2 to about 12,000
N/mm.sup.2. For example, the first conductive particles may include
cores containing silica (SiO.sub.2) or a silica composite.
[0030] In some embodiments, the cores of the first conductive
particles may include at least silica. As used herein, the silica
composite for the cores of the first conductive particles refers to
a composite of a polymer resin and silicon oxide (SiO.sub.2).
[0031] In the composite of the polymer resin and silica, the
polymer resin may include a polymer of at least one monomer
selected from the group of crosslinking polymerizable monomers and
monofunctional monomers. The polymer resin may be present in an
amount of about 10 wt % to about 85 wt % based on a total weight of
the composite. The polymer resin may be highly cross-linked organic
polymer particles having a high degree of crosslinking. The silica
may be present in an amount of about 15 w% to about 90 wt % based
on the total weight of the composite. The silica may represent the
remainder of the composite. The silica may be dispersed throughout,
e.g., randomly throughout, the polymer resin in the composite.
[0032] For example, the crosslinking polymerizable monomer may
include at least one selected from the group of vinyl benzene
monomers such as divinyl benzene; allyl compounds such as
1,4-divinyloxybutane, divinyl sulfone, diallyl phthalate, diallyl
acrylamide, triallyl (iso)cyanurate, and triallyl trimellitate;
acrylate monomers, such as ethylene glycol di(meth)acrylate,
propylene glycol di(meth)acrylate, pentaerythritol
tetra(meth)acrylate, pentaerythritol tri(meth)acrylate,
pentaerythritol di(meth)acrylate, trimethylolpropane
tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
dipentaerythritol penta(meth)acrylate, and glycerol
tri(meth)acrylate, and the like, without being limited thereto.
[0033] For example, the mono-functional monomer may include at
least one selected from the group of styrene monomers, such as
styrene, methylstyrene, m-chloromethylstyrene, and ethylstyrene;
(meth)acrylate monomers, such as methyl(meth)acrylate,
ethyl(meth)acrylate, propyl(meth)acrylate, n-butyl(meth)acrylate,
isobutyl(meth)acrylate, t-butyl(meth)acrylate,
2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate,
lauryl(meth)acrylate, and stearyl(meth)acrylate; vinyl monomers
such as vinyl chloride, vinyl acetate, vinyl ether, vinyl
propionate, vinyl butyrate, and the like, without being limited
thereto.
[0034] The silica composite may be obtained by adding silica to the
polymer resin. With the inclusion of the silica, the polymer resin
may have significantly improved physical properties in terms of,
e.g., strength, stiffness, and wear resistance. Accordingly, the
silica composite may be much harder than other typical polymer
resins. According to an exemplary embodiment, the silica composite
may be used as the core for conductive particles that are formed to
penetrate a metal oxide layer for connection within OLEDs.
[0035] The first conductive particle may further include a
conductive shell formed on the core, which core contains silica or
the silica composite. The first conductive particles may be
prepared as a single kind of conductive particle or by mixing two
or more kinds of conductive particles. The first conductive
particles may have an average particle size ranging from about 0.1
.mu.m to about 200 .mu.m.
[0036] In an implementation, each of the first conductive particles
may include protrusions formed on a surface thereof. For example,
the first conductive particle may include about 10 to about 40
protrusions per unit surface area (1 .mu.m.sup.2) thereof, e.g.,
about 15 to about 30 protrusions per unit surface area. Within this
range, the first conductive particles may exhibit excellent
connection performance.
[0037] In exemplary embodiments, a semiconductor device may be
connected by an anisotropic conductive film, which anisotropic
conductive film includes both the first conductive particles and
second conductive particles. For example, the first conductive
particles may be included in a first conductive layer, and the
second conductive particles may be included in a second conductive
layer so that the first and second conductive layers are discrete
layers. For example, referring to FIG. 8, a first conductive layer
100 has a second conductive layer 200 stacked thereon to form a
single anisotropic conductive film. According to another exemplary
embodiment, the first conductive particles may be intermixed with
the second conductive particles within the first conductive layer.
For example, referring to FIG. 9, the anisotropic conductive film
includes a first conductive layer 300, which includes both the
first conductive particles and the second conductive particles.
[0038] The first conductive particles may include cores containing
silica or the silica composite and a 20% K-value ranging from,
e.g., about 7,000 N/mm.sup.2 to about 12,000 N/mm.sup.2. The second
conductive particles may have a 20% K-value ranging from about
3,000 N/mm.sup.2 to about 7,000 N/mm.sup.2. A difference in 20%
K-value between the first conductive particles and the second
conductive particles may be less than about 5,000 N/mm.sup.2.
Further, the 20% K-value for the first conductive particles may be
greater than the 20% K-value for the second conductive
particles.
[0039] In this embodiment, the second conductive particles may have
a 20% K-value ranging from about 3,000 N/mm.sup.2 to about 7,000
N/mm.sup.2, e.g., about 4,500 N/mm.sup.2 to about 6,500 N/mm.sup.2.
Within this range, the conductive particles may exhibit suitable
deformability.
[0040] In this embodiment, the first conductive particles included
in the first conductive layer may have a high hardness and may act
as flow passages of electric current between circuit terminals. The
first conductive particles may not exhibit the characteristics of
damage and/or deformation thereof upon compression. Accordingly,
the first conductive particles may provide hardness to the
anisotropic conductive film. The second conductive particles, e.g.,
included in the second conductive layer or included in the first
conductive layer with the first conductive particles, may be easily
broken or deformed upon compression. Accordingly, the second
conductive parties may allow a degree of compression of the
anisotropic conductive film to be confirmed, e.g., to allow for
identification of a connection result of the anisotropic conductive
film.
[0041] The second conductive particles may be present in an amount
of about 1 to about 30 parts by weight based on 100 parts by weight
of all of the conductive particles. The first conductive particles
may represent a remainder of the weight of all of the conductive
particles, e.g., the first conductive particles may be present in
an amount of about 70 to about 99 parts by weight based on 100
parts by weight of all of the conductive particles. Accordingly, an
amount of the first conductive particles in the anisotropic
conductive film may be greater than the amount of second conductive
particles.
[0042] The difference in 20% K-value between the first conductive
particles and second conductive particles may be greater than 0 to
less than about 5,000 N/mm.sup.2. When the difference in 20%
K-value therebetween is less than about 5,000 N/mm.sup.2, an
increase in connection resistance due to excessive differences
between the first and second conductive particles may be avoided,
thereby deterioration in connection performance may not be
observed. If the first and second conductive particles have a same
20% K-value, a difference in hardness is not realized.
[0043] The second conductive particles may include suitable
conductive particles, which may include conductive particles that
have a 20% K-value ranging from about 3,000 N/mm.sup.2 to about
7,000 N/mm.sup.2, or exhibit a similar level of hardness.
[0044] Examples of the second conductive particles may include at
least one selected from the group of metallic particles including
Au, Ag, Ni, Cu, solder, and the like; carbon particles;
metal-coated resin particles prepared by coating resin particles,
such polyethylene, polypropylene, polyester, polystyrene, and
polyvinyl alcohol resin particles, or modified resin particles
thereof with metal such as Au, Ag, Ni, and the like; and
insulation-treated conductive particles prepared by coating such
conductive particles with insulator particles, without being
limited thereto. According to an exemplary embodiment, the second
conductive particles may include cores of a polymer resin, e.g., a
polymethyl methacrylate and/or a polysiloxane resin.
[0045] The second conductive particles may be prepared as a single
kind of conductive particle or by mixing two or more kinds of
conductive particles.
[0046] In exemplary embodiments, the first conductive particles
included in the first conductive layer may have high hardness and
may act as flow passages of electric current between circuit
terminals without damage or deformation of the first conductive
particles upon compression. Further, the second conductive
particles included in the second conductive layer may be easily
broken or deformed upon compression, thereby allowing the degree of
compression of the anisotropic conductive film to be confirmed.
[0047] The first conductive particles may have a higher surface
roughness (see FIG. 4) than that of the second conductive particles
(see FIG. 5). For example, referring to FIG. 4, the first
conductive particles may have the protrusions formed on a surface
thereof to form a rough outer surface having a high surface
roughness. Referring to FIG. 5, the second conductive particles may
appear smoother, e.g., the second conductive particles may
substantially exclude surface protrusions so as to be substantially
smooth.
[0048] When the surface roughness of the second conductive
particles is lower than the surface roughness of the first
conductive particles, it is possible to improve visibility of the
particles by reducing and/or preventing diffuse reflection of
light. The surface roughness of the first and second conductive
particles may be determined according to various factors such as
materials and preparation methods thereof. For example, when the
protrusions are formed on the surfaces of the first conductive
particles, the first conductive particles may have increased
surface roughness. Each of the protrusions of the first conductive
particles may protrude at a height of about 0.1 .mu.m or more,
e.g., 0.2 .mu.m or more, from an outer surface of the corresponding
conductive particle. The protrusions may protrude from the
conductive shell formed on the core containing the silica or the
silica composite of the first conductive particles.
[0049] Various processes, e.g., any process that which is a in the
art, may be used to form the protrusions on the surfaces of the
conductive particles, without limitation. For example, electroless
plating may be performed by dipping microspheres of a
core-conductive shell structure of the first conductive particles
into an electroless plating solution containing a metal salt
solution and a reducing agent.
[0050] The first conductive particle may include about 10 to about
40 protrusions per unit surface area (1 .mu.m.sup.2) thereof, e.g.,
about 15 to about 30 protrusions per unit surface area. Within this
range, the first conductive particles may exhibit excellent
connection performance.
[0051] The second conductive particles may have protrusions or may
not have protrusions on the surfaces thereof. In the case that the
second conductive particles include protrusions, the second
conductive particles may include a lesser amount of protrusions
than the first conductive particles.
[0052] The second conductive particle may include 0 to about 10
protrusions per unit surface area (1 .mu.m.sup.2) thereof, e.g., 0
to about 5 protrusions per unit surface area. Within this range of
the protrusions, it is possible to confirm suitable connection upon
bonding of the conductive film, thereby providing excellent
visibility to confirm suitable bonding pressure while reducing
connection resistance through operation of the protrusions.
[0053] As used herein, the term "visibility" related to the
particles refers to properties of an object allowing an observer to
view the object with the naked eye or using a microscope. In
addition, as used herein, the term "visibility" related to the
second conductive particles refer to properties of conductive
particles allowing an observer to observe deformation of the
conductive particles in order to confirm whether suitable
connection is obtained upon bonding of the anisotropic conductive
film.
[0054] Since the second conductive particles have relatively low
hardness compared to the first conductive particles, the second
conductive particles may facilitate confirmation of a suitable
connection of the anisotropic conductive film through easy
deformation, that is, excellent visibility with respect to
observing a connection result.
[0055] For example, when observing conductive particles having
large number of protrusions formed on the surfaces thereof using a
microscope or the like, the surfaces of the conductive particles
appear dark, thereby making it difficult to observe deformation of
the conductive particles. On the other hand, when observing
conductive particles having no protrusions or small amounts of
protrusions formed on the surfaces thereof, the surfaces of the
conductive particles appear bright, thereby facilitating
observation of deformation thereof (see FIG. 1 and FIG. 2).
[0056] In a further exemplary embodiment, a semiconductor device
may be connected by an anisotropic conductive film, in which the
anisotropic conductive film includes a first conductive layer
including first conductive particles, and a second conductive layer
formed on the first conductive layer and including second
conductive particles. The first conductive particles may include
cores containing silica or a silica composite and may have a 20%
K-value ranging from about 7,000 N/mm.sup.2 to about 12,000
N/mm.sup.2. The first conductive particles may have a higher
hardness than the second conductive particles.
[0057] In this exemplary embodiment, the difference in 20% K-value
between the first conductive particles and the second conductive
particles may be about 5,000 N/mm.sup.2 or more. The second
conductive particles may be easily broken or deformed upon
compression, thereby improving visibility of the conductive
particles by allowing the degree of compression of the anisotropic
conductive film to be confirmed. When the difference in 20% K-value
therebetween is greater than or equal to about 5,000 N/mm.sup.2,
the anisotropic conductive film may be easily deformed upon
compression, thereby facilitating improvement of visibility.
[0058] In this embodiment, the first conductive particles included
in the first conductive layer may have high hardness and may act as
flow passages of electric current between circuit terminals without
damage or deformation of the particles upon compression. The second
conductive particles included in the second conductive layer may be
easily broken or deformed upon compression, thereby allowing the
degree of compression of the anisotropic conductive film to be
confirmed.
[0059] When both the first conductive particles and the second
conductive particles are included in a single layer of the
anisotropic conductive film, the second conductive particles may
deteriorate flowability and tack of a composition for the
anisotropic conductive film and dispersibility during a process. As
a result, e.g., due to the deteriorated flowability of the
composition, temperature may be increased upon pre-compression in
order to obtain desired pre-compression performance. Thus, the
first and second conductive particles may be included in the first
and second conductive layers, respectively, in terms of
dispersibility, pre-compression temperature, viscosity, and
flowability.
[0060] For example, as the second conductive particles are included
in the second conductive layer, the first conductive particles may
have an improved degree of dispersion in the first conductive
layer. The degree of dispersion of the anisotropic conductive film
may be obtained by particle density. The anisotropic conductive
film may have a degree of dispersion ranging from about 20,000 to
about 70,000, e.g., from about 30,000 to about 60,000. The degree
of dispersion may be confirmed by the density of particles after
film coating, and the density of particles is calculated by the
following Equation 2 based on the number of particles counted by
KAMSCOPE after photographing the particles using a microscope.
Degree of dispersion=(Number of second conductive particles/Number
of first conductive particles).times.100 <Equation 2>
[0061] In an exemplary embodiment, the first conductive particles
may be present in an amount of about 1 wt % to about 30 wt % based
on a total amount of the composition for forming the first
conductive layer. The second conductive particles may be present in
an amount of about 1 wt % to about 30 wt % based on a total amount
of the composition for forming the second conductive layer.
[0062] The first conductive particles and/or second conductive
particles may be prepared by coating core compounds with conductive
metals. The core compound for the first conductive particles may
have a higher hardness than the core compound for the second
conductive particles. For example, the core compound for the first
conductive particles may be any core compound that provides a 20%
K-value of about 7,000 N/mm.sup.2 to about 12,000 N/mm.sup.2 to the
conductive particles. According to an exemplary embodiment, the
core compound for the first conductive particles may include silica
(SiO.sub.2) or a silica composite.
[0063] The core compound for the second conductive particles may
include at least one resin, such as epoxy, melamine, urethane,
benzoguanamine, phenol, poly olefin, polyether, polyester,
polystyrene, NBR, SBR, BR, polyvinyl alcohol, and polysilicone
resins, or modified resins thereof. According to another
embodiment, the second conducive particles may be prepared by
coating such resin particles with at least one metal such as gold,
silver, nickel, copper, palladium, solder, and the like. The second
conductive particles may be prepared using at least one selected
from among these core compounds.
[0064] In yet another exemplary embodiment, a semiconductor device
may be connected by an anisotropic conductive film, in which the
anisotropic conductive film includes a first conductive layer
including first conductive particles, and a second conductive layer
formed on the first conductive layer and including second
conductive particles. The first conductive particles may include
cores containing silica or a silica composite and may have a 20%
K-value ranging from about 7,000 N/mm.sup.2 to about 12,000
N/mm.sup.2. The first conductive particles may have a higher
surface roughness than the second conductive particles.
[0065] In this embodiment, the surface roughness of the first
conductive particles (see FIG. 4) may be greater than that of the
second conductive particles (see FIG. 5). When the surface
roughness of the second conductive particles is lower than the
surface roughness of the first conductive particles, it may be
possible to improve visibility of the particles by reducing and/or
preventing diffuse reflection of light.
[0066] In this embodiment, the surface roughness of the first and
second conductive particles may be confirmed through SEM
analysis.
[0067] The surface roughness of the first and second conductive
particles may be determined according to various factors such as
materials and preparation methods thereof. For example, when
protrusions are formed on the surfaces of the first conductive
particles, the first conductive particles may have increased
surface roughness. For example, any process known in the art may be
used to form the protrusions on the surfaces of the conductive
particles, without limitation.
[0068] An exemplary method of forming the protrusions includes
electroless plating, which may be performed by dipping microspheres
of a core-conductive shell structure into an electroless plating
solution containing a metal salt solution and a reducing agent.
Each of the protrusions of the first conductive particles may
protrude at a height of about 0.1 .mu.m or more, e.g., about 0.2
.mu.m or more, from an outer surface of the corresponding
conductive particle.
[0069] In this embodiment, the first and second conductive
particles having different hardness may have an average particle
diameter depending on the pitch of circuits. For example, the first
and second conductive particles may have an average particle
diameter of about 2 .mu.m to about 30 .mu.m, e.g., about 2 .mu.m to
about 6 .mu.m. The first conductive particles may have the same or
different particle diameter than the second conductive particles.
When the circuit has a fine pitch, the first conductive particles
have a smaller average particle diameter than the second conductive
particles.
[0070] In this embodiment, the first conductive particles may be
present in an amount of about 1 wt % to about 30 wt % based on the
total amount of the composition for the first conductive layer, and
the second conductive particles may be present in an amount of 1 wt
% to 30 wt % based on the total amount of the composition for the
second conductive layer.
[0071] The first conductive particles may include about 10 to about
40 protrusions per unit surface area (1 .mu.m.sup.2) thereof, e.g.,
about 15 to about 30 protrusions per unit surface area. Within this
range, the first conductive particles may exhibit excellent
connection performance.
[0072] The second conductive particles may or may not have
protrusions on the surfaces thereof. The second conductive particle
may include 0 to about 10 protrusions per unit surface area (1
.mu.m.sup.2) thereof, e.g., 0 to about 5 protrusions per unit
surface area. Within this range of the protrusions, it may be
possible to confirm suitable connection upon bonding of the
conductive film, thereby providing excellent visibility to confirm
suitable bonding pressure while possibly reducing connection
resistance via the protrusions.
[0073] In an exemplary embodiment of using an anisotropic
conductive film according to embodiments, a semiconductor device
may include a wiring substrate having a metal and metal oxide layer
placed on the outermost layer thereof, the anisotropic conductive
film attached to a chip mounting surface of the wiring substrate,
and a semiconductor chip mounted on the anisotropic conductive
film. The anisotropic conductive film may directly adjoin the metal
and metal oxide layer, and may include a first conductive layer
including first conductive particles. The first conductive
particles may have a 20% K-value ranging from about 7,000
N/mm.sup.2 to about 12,000 N/mm.sup.2 and a compressive strain
ranging from about 5% to about 40% upon thermal compression at
220.degree. C. under a load of 110 Mpa for 5 seconds.
[0074] To enhance the possibility of achieving a stable
maximization of a contact area between electrodes, while providing
suitable connection between the electrodes, it is sought for the
conductive microsphere to exhibit high hardness at an initial stage
of compression and to be suitably deformed as compression
proceeds.
[0075] According to this embodiment, the conductive microspheres
may have a 20% K-value from about 7,000 N/mm.sup.2 to about 12,000
N/mm.sup.2, e.g., from about 8,000 N/mm.sup.2 to about 11,000
N/mm.sup.2. Within this range of the 20% K-value, the conductive
microspheres may provide suitable connection through metal at the
uppermost layer of a terminal on a panel. If the 20% K-value of the
conductive microspheres is equal to or greater than about 7,000
N/mm.sup.2, the conductive microspheres may be sufficiently hard
and may provide a suitable connection through a metal oxide layer
of the terminal. Accordingly, a stable connection may result. If
the 20% K-value of the conductive microspheres equal to or less
than about 12,000 N/mm.sup.2, the conductive microspheres
interposed between the electrodes may be easily deformed, such that
the contact area between the electrode surface and the conductive
microspheres may be sufficiently enlarged, and it possible to
decrease connection resistance.
[0076] If the compressive strain is less than about 5%, compressive
force may be directly transferred to each of the panel and a driver
IC, causing physical damage thereof, thereby causing connection
failure. If the compressive strain exceeds about 40%, it may be
difficult for the conductive microspheres to be sufficiently
recovered upon contraction/expansion of adhesives by external heat.
Accordingly, a gap may be undesirably generated between the
conductive microspheres and the electrode surface.
[0077] The compressive strain may be calculated by the following
equation:
compressive strain=(R1-R2)/(R1+R2).times.100,
[0078] wherein R1 and R2 indicate a horizontal diameter and a
vertical diameter of a particle, respectively, when the particle is
deformed upon thermal compression of an anisotropic conductive film
at 220.degree. C. under a load of 110 MPa for 5 seconds.
[0079] In this embodiment, the first conductive particles may
include cores containing silica or a silica composite. When the
silica is added to a polymer resin, the polymer resin may have
significantly enhanced strength, stiffness, and wear resistance.
Further, as compared with the case where silica composite are used
as the cores, the first conductive particles including the polymer
resin have a certain degree of elasticity and thus may exhibit
flexible compression and deformation in a connection space.
[0080] In an exemplary embodiment, SiO.sub.2 may be present in an
amount of about 15 wt % to about 90 wt % based on the total amount
of the composite of the polymer resin and SiO.sub.2. Within this
range, the conductive microspheres may have desired hardness and
connection reliability.
[0081] In this embodiment, the first conductive layer may further
include second conductive particles, which have a lower 20% K-value
than the first conductive particles.
[0082] Further, in this embodiment, the anisotropic conductive film
may further include a second conductive layer, which is formed on
the first conductive layer and includes second conductive particles
having a lower 20% K-value than the first conductive particles. The
first conductive particles may have protrusions formed on surfaces
thereof.
[0083] The composition for the anisotropic conductive film may
further include an insulation adhesive component and a curing
agent. As for the insulation adhesive component, any typical
component used in compositions for anisotropic conductive films may
be used without limitation. For example, the insulation adhesive
component may include at least one selected from the group of
olefin resins, such as polyethylene, polypropylene, and the like;
butadiene resins, an acrylonitrile butadiene copolymer, a carboxyl
terminated acrylonitrile butadiene copolymer, polyimide resins,
polyamide resins, polyester resins, polyvinyl butylal resins,
ethylene-vinyl acetate copolymers, styrene-butylene-styrene (SBS),
styrene-ethylene-butylene-styrene (SEBS), acrylonitrile butadiene
rubber (NBR), epoxy resins, urethane resins, (meth)acrylic resins,
phenoxy resins, and the like, without being limited thereto. These
may be used alone or in combination thereof.
[0084] The curing agent may promote a curing reaction, thereby
ensuring adhesion between connection layers and connection
reliability. The curing agent may include a radical curable unit
selected from mono-functional or poly-functional (meth)acrylate
oligomers and monomers. For example, a bi-functional (meth)acrylate
monomer or oligomer may be used as the curing agent.
[0085] The curing system may include at least one selected from
epoxy (meth)acrylate resins, the intermolecular structure of which
includes a backbone of 2-bromohydroquinone, resorcinol, catechol,
bisphenols such as bisphenol A, bisphenol F, bisphenol AD and
bisphenol S, 4,4'-dihydroxybiphenyl, or bis(4-hydroxyphenyl)ether;
and (meth)acrylate oligomers comprising an alkyl, aryl, methylol,
allyl, cycloaliphatic, halogen (tetrabromo bisphenol A), or nitro
group; and a polycyclic aromatic ring-containing epoxy resin,
without being limited thereto.
[0086] A latent curing agent may be used, and may include an
epoxy-type heat curing agent, without being limited thereto. For
example, an epoxy-type heat curing agent known in the art may be
used without limitation. The epoxy-type heat curing agent may
include at least one selected from the group of imidazole, acid
anhydride, amine, hydrazine, cationic curing agents, and
combinations thereof
[0087] The composition for the anisotropic conductive film may
further include hydrophobic nanosilica. The hydrophobic nanosilica
may allow smooth adjustment of flowability under process conditions
and may induce high strength of the cured structure of the
anisotropic conductive film to reduce the possibility of and/or
prevent expansion of the anisotropic conductive film at high
temperature. The anisotropic conductive film may exhibit excellent
initial adhesion and low connection resistance while maintaining
connection and adhesion reliability under high temperature/high
humidity and thermal impact conditions, thereby ensuring excellent
durability for a long period of time.
[0088] The hydrophobic nanosilica particles may be prepared by
surface treatment of an organic silane compound, and may have a
particle size of about 5 nm to about 20 nm and a specific surface
area of about 100 m.sup.2/g to about 300 m.sup.2/g. The silica
particles may include at least one selected from Aerosil R-812,
Aerosil R-972, Aerosil R-805, Aerosil R-202, Aerosil R-8200
(Degussa GmbH), and the like, without being limited thereto.
[0089] The organic silane compound used for surface treatment of
nanosilica particles to exhibit hydrophobic properties may include
at least one selected from the group of vinyltrichlorosilane,
vinyltrimethoxysilane, 3-glycydoxypropyltrimethoxysilane,
3-methacryloxypropyltrimethoxysilane, dimethyldichlorosilane,
octylsilane, hexamethyldisilazane, octamethylchlorotetrasiloxane,
polydimethylsiloxane,
2-aminoethyl-3-aminopropylmethyldimethoxysilane,
3-ureidopropyltriethoxysilane, and the like.
[0090] The composition for the anisotropic conductive film may be
used for, e.g., a COG ACF (a chip-on-glass anisotropic conductive
film) for OLED devices (organic light emitting diode display
devices).
[0091] Next, the constitution and operation of embodiments will be
described in more detail with reference to examples. It should be
understood that the following examples are provided for
illustration only and are not to be construed in any way as
limiting. Accordingly, the following Examples and Comparative
Examples are provided in order to highlight characteristics of one
or more embodiments, but it will be understood that the Examples
and Comparative Examples are not to be construed as limiting the
scope of the embodiments, nor are the Comparative Examples to be
construed as being outside the scope of the embodiments. Further,
it will be understood that the embodiments are not limited to the
particular details described in the Examples and Comparative
Examples.
EXAMPLE 1
[0092] Preparation of anisotropic conductive film including two
types of conductive particles having different hardness and surface
protrusion density.
[0093] A composition for an anisotropic conductive film was
prepared using the following components:
[0094] based on 100 parts by weight of anisotropic conductive film
in terms of solid content,
[0095] 1) Epoxy: 17 parts by weight of BPA (Bisphenol A) epoxy
(Kukdo Chemical Co., Ltd.) and 19 parts by weight of polycyclic
aromatic ring-containing epoxy resin (HP4032D, Dainippon Ink and
Chemicals Inc.);
[0096] 2) Silica particles: 4 parts by weight of nanosilica (R812,
Degussa GmbH);
[0097] 3) Curing agent: 35 parts by weight of core-shell type
latent curing agent containing imidazole (Asahi Kasei Co.,
Ltd.);
[0098] 4) First conductive particles: 29 parts by weight of nickel
coated composite of the polymer resin and the silica (20% K-value:
10,000 N/mm.sup.2, compressive strain: 15% upon thermal compression
at 220.degree. C. under a load of 110 MPa for 5 seconds, surface
density of protrusion: 20/.mu.m.sup.2); and
[0099] 5) Second conductive particles: 6 part by weight of nickel
coated polymer resin conductive particles (20% K-value: 6,000
N/mm.sup.2, compressive strain: 25% upon thermal compression at
220.degree. C. under a load of 110 MPa for 5 seconds; surface
density of protrusion: 4/.mu.m.sup.2, Sekisui).
[0100] The prepared liquid composition was stirred at room
temperature (25.degree. C.) at a rate which could prevent
pulverization of the conductive particles. The stirred mixture was
thinly coated on a polyethylene terephthalate (PET) base film,
which had been subjected to silicon surface release treatment, and
dried by blowing hot air thereupon at 70.degree. C. for 5 minutes
to produce a 30 .mu.m thick film. For fabrication of the film, a
casting knife was used.
COMPARATIVE EXAMPLE 1
[0101] Preparation of anisotropic conductive film including only
first conductive particles as conductive particles
[0102] An anisotropic conductive film was prepared in the same
manner as in
[0103] Example 1 except that the second conductive particles were
not used and 35 parts by weight of the first conductive particles
was used.
COMPARATIVE EXAMPLE 2
[0104] Preparation of anisotropic conductive film including only
second conductive particles as conductive particles.
[0105] An anisotropic conductive film was prepared in the same
manner as in Example 1 except that the first conductive particles
were not used and 35 parts by weight of the second conductive
particles was used.
[0106] Table 1 shows the compositions of the anisotropic conductive
films prepared in Example 1, and Comparative Examples 1 and 2 in
terms of parts by weight.
TABLE-US-00001 TABLE 1 Comparative Comparative Composition Example
1 Example 1 Example 2 BPA epoxy 17 17 17 HP4032D 19 19 19
Nanosilica 4 4 4 Curing agent 35 35 35 First conductive 29 35 --
particles Second conductive 6 -- 35 particles Total 100 100 100
EXPERIMENTAL EXAMPLE 1
[0107] Measurement of Initial and Reliability Connection
Resistance
[0108] To measure connection resistance of the anisotropic
conductive films prepared in Example 1, and Comparative Examples 1
and 2, each of the anisotropic conductive films of Example 1, and
Comparative Examples 1 and 2 was interposed between a glass
substrate having a bump area of 2,000 .mu.m.sup.2 and a 2,000 .ANG.
thick titanium circuit and a 1.7 mm thick chip having a bump area
of 2,000 .mu.m2. Followed by compression and heating under
conditions of 220.degree. C. and 90 MPa for 5 seconds, thereby
preparing 5 specimens for each of the 4 anisotropic conductive film
samples.
[0109] 1) Pre-compression condition: 70.degree. C., 1 second, 1.0
MPa
[0110] 2) Main-compression condition: 220.degree. C., 5 seconds, 90
MPa
[0111] Initial connection resistance of each of the 5 specimens was
measured using a 4-point probe method (corresponding to ASTM
F43-64T), and an average initial connection resistance was
calculated.
[0112] In addition, each of the 5 specimens was left at 85.degree.
C. and 85% RH for 500 hours for high temperature/high humidity
reliability evaluation, and reliability connection resistance of
each of the 5 specimens was measured according to ASTM D117 to
obtain an average value thereof.
[0113] Table 2 shows measurement results of the initial and
reliability connection resistance of the anisotropic conductive
films prepared in Example 1 and Comparative Examples 1 and 2.
TABLE-US-00002 TABLE 2 Compar- Cmpar- ative ative Example 1 Example
1 Example 2 Initial connection resistance (.OMEGA.) 0.34 0.28 5.1
Reliability connection resistance (.OMEGA.) 2.7 2.4 10.3
EXPERIMENTAL EXAMPLE 2
[0114] Evaluation of Visibility of Conductive Particles after Film
Bonding
[0115] To evaluate visibility of bonding of the anisotropic
conductive films of
[0116] Example 1, and Comparative Examples 1 and 2, each of the
anisotropic conductive films was compressed under conditions of
200.degree. C. and 4.0 MPa for 4 seconds, and evaluated as to
whether deformation of the conductive particles could be confirmed
through a microscope.
[0117] Evaluation results of visibility are provided with reference
to FIG. 2.
[0118] According to Experimental Examples 1 and 2, as the amount of
the first conductive particles exhibiting high hardness increased,
the connection resistance was decreased, thereby providing improved
connection performance. Accordingly, the anisotropic conductive
film of Comparative Example 1 containing the largest amount of the
first conductive particles exhibited superior connection
performance to other films. However, since the anisotropic
conductive film of Comparative Example 1 does not include the
second conductive particles, it did not exhibit visibility.
EXAMPLE 2
[0119] (1) Preparation of Composite of Polymer Resin and Silica
[0120] In a reactor, deionized water and a sodium lauryl sulfate
emulsifying agent were placed in weighed amounts, stirred at
70.degree. C. for 30 minutes under a nitrogen atmosphere, followed
by addition of 26 g of styrene (Junsei Co., Ltd) as a polymer
resin, 4 g of silica, and 1 g of a potassium persulfate aqueous
solution to the mixture, thereby preparing a composite of the
polymer resin and the silica having an average particle diameter of
2 .mu.m.
[0121] (2) Preparation of Conductive Microspheres
[0122] The prepared composite of the polymer resin and the silica
was etched in a chromium acid and sulfuric acid solution, dipped in
a nickel chloride solution to form fine nuclei of nickel on the
surface of the particles through reduction, followed by electroless
nickel plating to form a conductive metal layer. Then, Ni
microspheres having a diameter of 20 nm to 100 nm were deposited on
the conductive metal layer, followed by plating with at least one
of Au, Pd, and Ni, thereby preparing conductive microspheres.
[0123] (3) Preparation of Double-Layer Anisotropic Conductive
Film
[0124] Detailed components used in Examples and Comparative
Examples were as follows.
[0125] 1. Binder system: Bisphenol A-type epoxy resin (YP-50, Kukdo
Chemical Co., Ltd.)
[0126] 2. Curing system: Polycyclic aromatic ring-containing epoxy
resin (HP4032D, Dainippon Ink and Chemical Inc.)
[0127] 3. Hydrophobic nanosilica: Nanosilica (R812, Degussa
GmbH)
[0128] 4. Latent curing agent: Imidazole microcapsule type
((HX3922HP, Asahi Kasei Co., Ltd.)
[0129] 5. Conductive microsphere 1: Composite of nickel coated
polymer resin and silica prepared in Example 2-(2) (20% K-value:
10,000 N/mm.sup.2, compressive strain: 15% upon thermal compression
at 220.degree. C. under a load of 110 MPa for 5 seconds)
[0130] 6. Conductive microsphere 2: Nickel coated polymer resin
conductive particles (20% K-value: 5,000 N/mm.sup.2, compressive
strain: 30% upon thermal compression at 220.degree. C. under a load
of 110 MPa for 5 seconds, Sekisui)
[0131] 7. Conductive microsphere 3: Nickel coated polymer resin
conductive particles (20% K-value: 2,000 N/mm.sup.2, compressive
strain: 3% upon thermal compression at 220.degree. C. under a load
of 110 MPa for 5 seconds, NCI)
[0132] 8. Silane coupling agent:
gamma-glycidoxytrimethoxysilane
[0133] 9. Solution for silane surface treatment: Solution prepared
by diluting the binder system and
gamma-glycidoxypropyltrimethoxysilane in a mixing ratio of 2:1 in a
solvent to a concentration of 10%
[0134] 10. Core-shell rubber: Butadiene rubber (Gantz)
[0135] Preparation of Anisotropic Conductive Film (ACF)
[0136] The binder system, the curing system, the conductive
microspheres prepared in
[0137] Example 2-(2), the silica, the latent curing agent, and the
silane coupling agent were mixed in amounts as listed in Table 3
with 50 parts by weight of a solvent (PGMEA), thereby preparing a
composition for an anisotropic conductive film. The composition was
coated to a thickness of 20 .mu.m on a base film, and 0.1 ml of the
solution for silane surface treatment was uniformly sprayed to the
surface of the film. Then, the composition was dried at 70.degree.
C. for 5 minutes, thereby preparing a desired anisotropic
conductive film.
[0138] b. Preparation of Non-Conductive Film (NCF)
[0139] The binder system, the curing system, the silica, the latent
curing agent, and the silane coupling agent were mixed in amounts
as listed in Table 3 with 50 parts by weight of a solvent (PGMEA),
thereby preparing a composition for an insulation adhesive layer.
Then, the composition was coated to a thickness of 10 .mu.m on a
base film. Then, the composition was dried at 70.degree. C. for 5
minutes, thereby preparing a non-conductive film of the anisotropic
conductive film.
[0140] c. Preparation of Double-Layer Anisotropic Conductive
Film
[0141] The prepared conductive anisotropic conductive film and
non-conductive film were bonded to each other at 40.degree. C.
under a load of 1 MPa through a laminating process, thereby
preparing a double-layer anisotropic conductive film of Example 2
in which the anisotropic conductive film is stacked on the
non-conductive film.
COMPARATIVE EXAMPLES 3 AND 4
[0142] Double-layer anisotropic conductive films were prepared in
the same manner as in Example 2 except for the compositions as
listed in Table 3 (unit: wt % in solid content).
TABLE-US-00003 TABLE 3 ACF Exam- Comparative Comparative
Composition ple 2 Example 3 Example 4 NCF Binder system 17 17 17 26
Curing system 19 19 19 26 Hydrophobic nanosilica 4 4 4 3 Latent
curing agent 28 28 28 32 Conductive microsphere 1 30 Conductive
microsphere 2 30 Conductive microsphere 3 30 Silane coupling agent
2 2 2 2 Core shell rubber 0 0 0 10 Total 100 100 100 100
[0143] The films prepared in Example 2, and Comparative Examples 3
to 4, were evaluated as to connection resistance and
post-reliability test connection resistance of an ACF layer
according to the following method. Results are shown in Table
4.
[0144] <Evaluation of Physical Properties>
[0145] 1. Initial connection resistance: As adherents, a driver IC
chip having a bump area of 1,430 .mu.m.sup.2 and a glass substrate
having a 2,000 .ANG. thick circuit were used. Here, the uppermost
layer of terminals was comprised of titanium. Each of the prepared
films was placed between the adherents and thermally compressed
under conditions of 220.degree. C. and 110 MPa for 5 seconds to
prepare a sample. Electric resistance of the sample was measured by
applying an electric current of 1 mA using a HIOKI HI-tester (HIOKI
Co., Ltd.).
[0146] 2. Connection resistance after reliability test: The
prepared sample was left under conditions of high temperature and
high humidity (85.degree. C./85% RH) for 500 hours, and connection
resistance of the sample was measured by applying an electric
current of 1 mA using a HIOKI HI-tester (HIOKI Co., Ltd.).
TABLE-US-00004 TABLE 4 ACF Comparative Comparative Example 2
Example 3 Example 4 Connection resistance 0.28 0.82 0.29 (initial)
Connection resistance 2.4 5.7 5400 (after reliability test)
[0147] From Table 4, it could be seen that the conductive
microspheres and the anisotropic conductive film including the same
exhibited good electrical properties in terms of initial connection
resistance and post-reliability connection resistance.
EXAMPLE 3
Preparation of Double-Layer Anisotropic Conductive Film
[0148] (1) Preparation of Second Conductive Layer Film
[0149] 30 parts by weight of a binder (YP50, Kukdo Chemical Co.,
Ltd.), 32 parts by weight of an epoxy resin (RKB4110, Resinous
Product Company), 1 part by weight of a coupling agent (KBM403,
Shinetsu Co., Ltd.), 27 parts by weight of a latent curing agent
(HX3941, Asahi Kasei Co., Ltd.), 5 parts by weight of second
conductive particles (AUEL003, Sekisui, 20% k-value: 1900
N/mm.sup.2), and 100 parts by weight of a solvent PGMEA were mixed.
Then, the prepared mixture was coated on a release film and dried
in an oven at 70.degree. C. to volatize the solvent, thereby
preparing a 10 .mu.m thick non-conductive film.
[0150] (2) Preparation of First Conductive Layer Film
[0151] 23 parts by weight of a binder (YP50, Kukdo Chemical Co.,
Ltd.), 26 parts by weight of a liquid epoxy resin (RKB4110,
Resinous Product Company), 1 part by weight of a coupling agent
(KBM403, ShinEtsu Co., Ltd.), 20 parts by weight of a latent curing
agent (HX3941, Asahi Kasei Co., Ltd.), 30 parts by weight of first
conductive particles (PNR and Nippon Chemical Industry, 20%
k-value: 7000 N/mm.sup.2), and 100 parts by weight of a solvent
PGMEA were mixed. Then, the prepared mixture was coated on a
release film and dried in an oven at 70.degree. C. to volatize the
solvent, thereby preparing a 10 .mu.m thick anisotropic conductive
film.
[0152] (3) Preparation of Double-Layer Anisotropic Conductive
Film
[0153] The prepared first conductive layer film and the second
conductive layer films were bonded to each other under conditions
of 40.degree. C. and 0.2 Mpa through a laminating process, thereby
preparing a double-layer anisotropic conductive film of Example 3
in which the anisotropic conductive film is stacked on the
non-conductive film.
EXAMPLE 4
Preparation of Double-Layer Anisotropic Conductive Film
[0154] A double-layer anisotropic conductive film was prepared in
the same manner as in Example 3 except that the second conductive
particles were added in an amount of 10 parts by weight.
EXAMPLE 5
Preparation of Double-Layer Anisotropic Conductive Film
[0155] A double-layer anisotropic conductive film was prepared in
the same manner as in Example 3 except that the second conductive
particles were added in an amount of 15 parts by weight.
COMPARATIVE EXAMPLES 5 TO 8
[0156] Double-layer anisotropic conductive films were prepared in
the same manner as in Example 3 except for the compositions as
listed in Table 3 (unit: wt % in solid content).
TABLE-US-00005 TABLE 5 Comparative Comparative Comparative
Comparative Example 3 Example 4 Example 5 Example 5 Example 6
Example 7 Example 8 ACF A 23 23 23 23 23 23 23 layer B 26 26 26 26
26 26 26 C 1 1 1 1 1 1 1 D 20 20 20 20 20 20 20 E 30 30 30 30 30 30
30 F -- -- -- 5 10 15 NCF A 30 30 30 30 30 30 30 layer B 32 32 32
32 32 32 32 C 1 1 1 1 1 1 1 D 27 27 27 27 27 27 27 F 5 10 15 A:
Binder-Phenoxy resin (YP50, Kukdo Chemical Co., Ltd.) B: Epoxy
resin (RKB, Resinous Product Company) C: Silane coupling agent
(KBM403, Shinetsu Co., Ltd.) D: Latent curing agent-Imidazole
curing agent (HX3941, Asahi Kasei Co., Ltd.) E: First conductive
particles (PNR, Japan Chemical Industry Inc.)-(20% k-value: 7000
N/mm.sup.2) F: Second conductive particles (AUEL003, Sekisui)-(20%
k-value: 1900 N/mm.sup.2)
[0157] The prepared compositions and film of Examples 3 to 5 and
Comparative Examples 5 to 8 were evaluated as to ACF viscosity, ACF
coating state, degree of dispersion of the first conductive
particles/second conductive particles, pre-compression temperature,
post-bonding resistance and post-bonding visibility of particles by
the following methods. Results are shown in Table 6.
[0158] <Evaluation of Physical Properties>
[0159] (1) ACF viscosity: The viscosity of the composition of the
ACF before drying was measured using a No. 6 spindle of a
Brookfield viscometer at 25.degree. C. and 60 rpm.
[0160] (2) ACF coating state: Stripes, nodules, stains, dents,
scratches, and the like on the ACF upon coating were observed
through visual inspection with the naked eye. After coating, the
anisotropic conductive film was maintained in a thickness variation
of 1 micrometer or less and an area-based diameter of 1 mm or
less.
[0161] (3) Degree of dispersion of first conductive
particles/second conductive particles within ACF: After being
coated on the double-layer anisotropic conductive film, the number
of first conductive particles and the number of second conductive
particles were directly counted on a micrograph, and the degree of
dispersion was calculated by the following equation.
Degree of dispersion=(Number of second conductive particles/number
of first conductive particles).times.100
[0162] (4) Pre-compression temperature: It was confirmed through
visual inspection with the naked eye whether the ACF was suitably
attached to the panel when the base film was stripped off after
compressing the ACF while measuring the temperature of the ACF.
Table 2 shows the pre-compression temperature at which the ACF was
suitably attached to the panel. When the ACF was detached from the
panel due to low adhesion, the pre-compression temperature was
raised until the ACF remained in an attached state to the
panel.
[0163] (5) Post-bonding resistance: Each of the anisotropic
conductive films prepared in the examples and the comparative
examples was left at 25.degree. C. for 1 hour, followed by
evaluation of post-bonding resistance using a 50 .mu.m pitch OLB
TEG and TIO glass substrate, COF, and TCP (tape carrier package).
After pre-compressing the anisotropic conductive film on the
terminals of the OLB circuit under conditions of 50.degree. C. and
1 MPa for 1 second, the release film was removed. Then, the
anisotropic conductive film was subjected to main compression with
respect to the COF circuit terminals under conditions of
180.degree. C. and 3 MPa for 5 seconds. Seven specimens for each
sample were prepared, and employed to measure connection resistance
by a 4-point probe method (according to ASTM F43-64T).
[0164] (6) Post-bonding visibility of particles: After bonding,
breakage of the particles on the bumps was confirmed using an
optical microscope (Olympus Co., Ltd.), with windows open at
input/output terminals. When the particles were opaque, it was
determined that the particles exhibited poor visibility, and when
the particles were transparent, it was determined that the
particles exhibited good visibility. One example of good visibility
is shown in FIG. 6 (Example 4), and one example of poor visibility
is shown in FIG. 7 (Comparative Example 8).
TABLE-US-00006 TABLE 6 Comparative Comparative Comparative
Comparative Example 3 Example 4 Example 5 Example 5 Example 6
Example 7 Example 8 ACF viscosity 5,000 cps 5,000 cps 5,000 cps
8,000 cps 12,000 cps 15,000 cps 5,000 cps Filter Difficulty ACF
coating state .largecircle. .largecircle. .largecircle. .DELTA. X X
.largecircle. Stripe and Scratch dent Degree of dispersion 35000
.+-. 2000 35000 .+-. 2000 35000 .+-. 2000 41000 .+-. 5000 47000
.+-. 10000 Non- 35000 .+-. 2000 of first conductive uniform
particles/second dispersion conductive particles within ACF
Pre-compression 50.degree. C. or 50.degree. C. or 50.degree. C. or
80.degree. C. or 100.degree. C. or 120.degree. C. or 50.degree. C.
or temperature more more more more more more more Post-bonding 1
.OMEGA. or less 1 .OMEGA. or less 1 .OMEGA. or less 1 .OMEGA. or
less 1 .OMEGA. or less 1 .OMEGA. or less 1 .OMEGA. or less
resistance Post-bonding .circleincircle. .circleincircle.
.circleincircle. .largecircle. .largecircle. X X visibility
[0165] From Table 6, it could be seen that the anisotropic
conductive film according to Examples 3, 4, and 5, had improved
physical properties in terms of visibility, viscosity, dispersion,
and flowability, and also allowed pre-compression at low
temperature. Further, the anisotropic conductive film according to
embodiments had low pre-compression temperature, thereby providing
excellent adhesion and electrical properties including connection
resistance and insulation resistance.
[0166] By way of summation and review, anisotropic conductive
adhesives may be suitable to be used as connecting materials for
circuit terminals when forming circuit connections for various
displays and semiconductor devices. Further, conductive
microspheres have been made in the form of carbon fibers, solder
balls, and the like. The conductive microspheres may be prepared in
the form of metallic balls such as nickel or silver balls. Another
method of forming the conductive microspheres includes coating
spherical resin particles with nickel, gold or palladium, and/or by
processing the spherical resin particles with another material.
[0167] An anisotropic conductive film used for electrical
connection between a driver IC and a glass panel may be referred to
as a COG (chip-on-glass) ACF. Under conditions of high temperature
and high pressure, the COG ACF is bonded between the driver IC and
the glass panel such that gold bumps of the driver IC may be
electrically connected to terminals on the glass panel via deformed
conductive particles. Further, it is desirable that the conductive
particles of a COG ACF for LCDs have relatively low hardness and
the conductive particles of a COG ACF for OLEDs have relatively
high hardness. In this regard, for an LCD, in which the uppermost
layer of terminals on the panel may be composed of indium tin oxide
(ITO), the conductive particles having large deformability in a
suitable range may provide a wide contact area. For an OLED, in
which the uppermost layer of terminals on the panel may be composed
of metal, the conductive particles having high hardness may
penetrate an oxide layer on the metal.
[0168] Further, to identify whether a connection of an anisotropic
conductive film is successful, deformation of the conductive
particles may be observed. However, when hard conductive particles
are used, the conductive particles may not be substantially
deformed, thereby making it difficult to identify connection of the
anisotropic conductive film. Further, when a large number of
protrusions are formed on the surfaces of the particles, diffusive
reflection may occur on the surfaces of the particles, which makes
observation of the particles more difficult, thereby deteriorating
visibility.
[0169] In addition, conductive microspheres having high hardness
tend to exhibit low deformability upon compression and generate
compressive force when compressed between the terminals of the
panel and bumps of the driver IC. In this case, the compressive
force may be transferred to the panel and the driver IC, causing
physical damage and connection failure. Accordingly, the use of
conductive particles having high hardness and formed on the surface
thereof with a large number of protrusions results in low
visibility, thereby making identification of connection of the
anisotropic conductive film difficult.
[0170] In view of the above, embodiments relate to providing
conductive microspheres, which exhibit excellent electrical
connection performance, and an anisotropic conductive film
including the same. In this regard, to stably achieve maximization
of a contact area between electrodes, while ensuring good
connection therebetween, it is desirable for the particles to
exhibit hardness at an initial compression stage and to be suitably
deformed as compression proceeds.
[0171] Accordingly, embodiments relate to a semiconductor device
connected by an anisotropic conductive film including conductive
microspheres in which first conductive particles have high hardness
and second conductive particles have low hardness. Thus, the first
conductive particles may provide low connection resistance and the
second conductive particles permit identification of a connection
result and measurement of a suitable bonding pressure, thereby
providing enhanced connection performance and effective
visibility.
[0172] Embodiments also relate to a semiconductor device connected
by an anisotropic conductive film, in which a low visibility and
difficulty in identification of film connection due to
insignificant deformation of conductive particles in view of having
relatively high hardness and/or a relatively large number of
protrusions on surfaces thereof, may be avoided.
[0173] Embodiments further relate to providing conductive
microspheres and an anisotropic conductive film including the same,
which have sufficient hardness to penetrate a metal oxide layer to
provide good connectivity while exhibiting compression
deformability so as not to cause physical damage to terminals or
bumps. Accordingly, the conductive microspheres may provide an
increased contact area between connection substrates upon
compression, thereby providing excellent conductivity.
[0174] Example embodiments have been disclosed herein, and although
specific terms are employed, they are used and are to be
interpreted in a generic and descriptive sense only and not for
purpose of limitation. Accordingly, it will be understood by those
of skill in the art that various changes in form and details may be
made without departing from the spirit and scope of the present
invention as set forth in the following claims.
* * * * *